Conventionally, there has been well known a visual apparatus which is not arranged to visually examine an object directly with operator's eyes, but is arranged to display left and right images of the object picked up by left and right cameras on the-respective screens of left and right displays for the operator to visually examine the object on the left and right screens. With such an apparatus, even in a case where it is necessary for an operator to be at a location far away from an object at a dangerous working site, for example, the operator can control and operate the visual apparatus as if he operates with the direct visual examination of the object with his eyes.
The direct visual examination of an object by an operator and the visual examination by the above visual apparatus will be explained by referring to FIGS. 4 and 5.
First, as shown in FIG. 4, an operator can gaze at a center position C of a work WK1 by adjusting a parallax .theta..sub.1 -.theta..sub.2 of left and right eyes. In this case, angles .theta..sub.1 and .theta..sub.2 and the parallax vary depending on distances from the operator's eyes to the work WK1, however, the human's eyes unconsciously perform the adjustment. When the operator gazes at a center position D of a work WK2, such adjustment is performed similarly.
Meanwhile, in the case of the visual examination by the visual apparatus as shown in FIG. 5, the distances 11 and 12 between left and right cameras 21 and 22 and the center position C of the work WK1 are measured, and on the basis of the measured distances, the pick-up directions of the left and right cameras 21 and 22 are changed to the directions shown by arrows A and B to vary a parallax between the left and right cameras similar to the human eyes' parallax. In this case, the pick-up images taken by the left and right cameras 21 and 22 are displayed on screens 23a and 24a of display units 23 and 24 which correspond to human's left and right eyes, as shown in FIGS. 6(a) and 6(b).
As shown in FIGS. 6(a) and 6(b), when an X axis is set in a horizontal direction, the center position C of the work WK1 is located at an identical center position XC of the screens 23a and 24a. For this reason, so long as the operator's gazing point is on the work WK1, the left and right images coincide with each other, and thus the operator can visually examine the work naturally and without the sense of, fatigue, uncomfortableness and inconsistency as same to a situation where the operator visually examines the work with naked eyes.
However, there occurs such a case that the operator observes another object, for example, the work WK2 being displayed on the screen. In this case, the parallax of the left and right cameras 21 and 22 has been adjusted with respect to the work WK1 but not the work WK2, which results in that the center position D of the work WK2 on the left screen 23a is different from that on the right screen 24a, that is, the center positions D on the left and right screens 23a and 24a are displayed at different positions X1 and X2 (&gt;X1). The distance measurement is carried out with respect to a predetermined single point on the image that is usually different from the operator's observation point.
Accordingly, when the visual examination point is on the work WK2, the left and right images do not coincide with each other and the situation is different from the case when the operator observes the work with the naked eyes, so that the operator feels tired and uncomfortable and will visually examine the work with the sense of inconsistency. This involves such disadvantages as a deteriorated remote operation efficiency. With the conventional visual apparatus, since the distances between the cameras and object are measured and the parallax at the left and right camera sides is adjusted on the basis of the measured result, a device cost is involved for the distance measurement.
In view of the above circumstances, it is an object of the present invention to provide a visual apparatus which is so arranged that, even when an operator observes a given position on a screen, a visual examination without the sense of inconsistency can be performed to thereby improve a working efficiency to reduce the device cost without performing the distance measurement.